Benzotriazole and heterocyclic ketimide activators for leuco compounds



United States Patent 3 284,205 BENZOTRIAZOLE AI ID HETEROCYCLIC KETI- MIDE ACTIVATORS FOR LEUCO COMPOUNDS Robert H. Sprague, Chagrin Falls, John A. Stewart, Parma, and James M. Lewis, Cleveland, Ohio, assignors to Horizons Incorporated, Cleveland, Ohio, a corporation of New Jersey No Drawing. Filed Sept. 17, 1963, Ser. No. 309,407 11 Claims. (CI. 96-90) This invention relates to non-silver photosensitive compositions which print-out an image directly upon exposureto a suitable dosage of visible light, and to the use of such compositions as thin films in photographic processes. More particularly this invention relates to photosensitive compositions comprising at least one colorless leuco compound which when intimately admixed wit-h one or more colorless activator compounds, yields a mixture which when exposed to visible light prints out a visible image directly at speeds which are of practical significance, and to the processing of such compositions to yield a permanent useful image.

1. The leuco compounds The leuco compounds which may be utilized in accordance with the present invention comprise two recognized classes of dye forming colorless com-pounds, namely leuco base of diand triaryl-methane dyes and a second class of leuco compounds, namely leuco Xanthenes, leuco thioxantlhenes, leuco selenoxanthenes and leuco ac-nidenes.

The leuco bases of diand triarylmethane dyes which are usitable in the compositions about to be described more :fully are those represented by the general formula wherein each R is selected from the group consisting of H, lower alkyl and aryl and the several Rs may be the same or different, and R is selected from the group consisting of H, aryl, alkyl and particularly wherein each of the Rs is selected from the group consisting of H, alkyl and aryl.

Leuc-o dyes represented by the above formula which have been found suitable include:

leuco crystal violet leuco opal blue leuco malachite green leuco rosaniline leuco pararosaniline p,p,p"-trimethyl leuco opal blue p,p,p-trichloro leuco opal blue and other compounds of a similar nature.

The other class of leuco compounds which are suitable in the composition about to be described more fully, are generally similar to the leuco triaryl-methane dyes except that they are characterized by the presence of one or more bridging hetero atoms and therefore are ice compounds which may be represented by the general formulas RQ/ H wherein each R is selected from the group consisting of H, lower alkyl and aryl and may be the same or different and R is selected from the group consisting of H, alkyl and aryl, including particularly and wherein Z represents a member selected from the group consisting of O, S, Se and -NH.

As indicated, the preferred leuco compounds of this class are substituted in the 3,6 positions and include 3,6 bis (dimethylamino) 9 (p-dimethylaminophenyl) xanthene 3,6 bis (diethylamino) 9 (p dimet'hylaminopihenyl) xant hene 3,6 bis (diethylamino) 9 (p diethylarnin-oplie-nyl) 'xant hene 3,6 bis (dimeflhylamino) 9 (p-dimethylaminophenyl) thioxanthene 2. The activators A diverse group of colorless nitrogen-containing organic compounds have been founduseful in the present invention. In general these compounds fall into either of the two following groups:

A. Triaz-oles, i.e. heterocyclic compounds wherein there are three nitrogen atoms in a 5 membered heterocyclic nucleus.

B. Heterocyclic ketimides, i.e. compounds wherein an imide nitrogen (=NH) is attached to a ring carbon in a 5 or 6 membered heterocyclic nucleus.

While not wishing to be bound :by any specific theory it appears that the ketimide activators in the present invention are compounds capable of existence in two tutomeric forms of which the signfiicant fragment of the structure may center on the imide group, viz.

Hegero Nucleus G=NH Hetero O-NHr Nucleus In the results which follow the activators were: A. 3-naphthylisoxazolone imide 3. Evaluation procedure and results The data reported in the table which follows is the result of tests demonstrating the effect of visible light on mixtures of various leuco base and activators. In each of the five (5) compositions for which results are reported, the leuco compound was 3,6-bis-(dimethylamino) -9- (p-dimethylarnin-ophenyl xanthene hereinafter identified as D-l79. I

For each composition, equal volumes of acetone and a 10% by weight solution of polystyrene in benzene were mixed and then the indicated weight of the specified activator and an equal weight of D179 Were dissolved in the mixture. The resulting composition was coated by means of a Bird applicator on 500-D Mylar polyester in a coating having a wet thickness of 0.0015 inch. The coating was permitted to dry in air. Thereafter the com position was exposed (1) either to a General Electric No. 2 Reflector Photo Flood Lamp (RFL 2) through a step tablet or (2) using an Eastman Kodak No.10l Sensitomete with the light converted to equal mean noonday sun by means of a suitable filter (Eastman No. 78AA).

When the composition wa exposed to a General Electric 500 watt RFL2 Photofiood lamp exposure was through a #2 silver step wedge for a 5 minute interval at a distance of 12 inches from lamp to test materials. The density and number of steps visible in the image were read, after fixing the image by solvent wash or by heat.

When the composition was exposed on an Eastman Kodak No. 101 Sensitometer the light was converted by the use of a 78AA Filter, to equal mean noon day light. The resulting image was fixed by a solvent wash or by exposure to heat. Thereafter the density of the image was read and the LES. Was computed as described below.

The exposed material was stabilized by two or more successive rinses in a mixture of 1 part acetone and 4 parts petroleum ether, or by being maintained at 125 C. in a convention type oven for four (4) minutes. The stabilized material was reexposed 4 minutes to the RFLZ with no darkening. The densities in the resulting step wedge were read with an Eastman No. 1 Color Densitometer using the Green Filter, with the results reported below.

L.E.S. (abbreviation for Light Exposure Speed) refers to a speed rating system developed at the Wright Air Development Division of Air Research and Development Command (USAF), and is defined as the reciprocal of the exposure in meter candle seconds which is required to produce a double diffuse reflection density of 0.2 density units above base plus fog. As in the more conventional ASA system used to rate silver halide films, the higher the LES. number faster the film is.

Similarly, exposure to visible light of a mixture of leuco Crystal Violet and S-chlorobenzotuiazole gives a visible image and exposure to visible light of a mixture of leuco Crystal Violet and 3-naphthylisoxazolone imide gave a blue image of comparable density.

4 4. Fixing After exposure, the colored image produced may be fixed or stabilized either by a solvent rinse as described above or by mild heating.

The method of stabilization selected in any specific instance will depend to some extent upon the materials being used and it is to be noted that many of the slower compositions may be preferable to some of the faster compositions because some of the latter are less susceptible to heat or dry fixing than some of the former.

While not wishing to be bound by any specific theory as to the manner in which the exposure to visible light to an intimate mixture comprising two or more originally colorless compounds produced a colored image, it is believed that the final colored image Which forms in the light struck areas is always the dye which forms as a result of oxidation of the leuco base. Furthermore it appears that when the photosensitive mixtures is prepared, on mixing the compounds which are colorless, a weakly tinted mixture is formed.

It is also considered possible that the real active ingredient in the mixture is that very minute amount of an oxidized product which results when the leuco base is exposed to oxygen e.g. in the ordinary atmosphere.

Whatever the true mechanism each of the activators listed above, or mixtures of the same, bring about oxidation of the leuco compound upon exposure to a suitable dose of visible light and as a result form a direct visible print-out image in the light struck areas.

5. Proportions The relative proportions of the leuco dye bases and the activators for the same may be varied considerably from the weight proportions given by Way of illustration in the examples and are preferably within the range between 10 to 1 and 1 to 10 parts by weight.

As with other photosensitive compositions if not used at the time they are prepared the compositions of the present invention would be stored in cool dark relatively dry surroundings.

Having now described the invention in accordance With the patent statutes it is not intended that it be limited except as may be required by the appended claims.

We claim:

1. A composition which prints out a visible image directly as a result of exposure to visible light said composition comprising an intimate mixture consisting essentially of:

(1) at least one leuco compound selected from the group consisting of leuco compounds represented by one of the following general formulas R\ III R R R2 R wherein each R is a monovalent radical selected from the group consisting of H, lower alkyl and aryl and not all of the Rs need be the same and R is a monovalent radical selected from the group consisting of H, lower alkyl and aryl: and

wherein each R has the same meaning as indicated above and Z represents a member selected from the group consisting of O, S, Se and NH, and R is a monovalent radical selected from the group consisting of H, alkyl and aryl; and

(2) at least one colorless nitrogen-containing organic compound selected from the group consisting of henzotriazoles and heterocyclic ketimides in which the imide nitrogen is attached to a ring carbon in a 'heterocyclic nucleus having at least 5 and not more than 6 atoms.

2. The composition of claim 1 wherein the leuco compound is a leuco base of a triphenylmethane dye.

3. The composition of claim 1 in which the nitrogencontaining compound is benzotriazole.

4. The composition of claim 1 wherein the nitrogencontaining compound is an isoxazolone imide.

5. The composition of claim 1 wherein the leuco base is 3,6-b-is(dimethylamtino)9-(p-dimethylamino phenyl) Xanthene.

6. A dry film consisting of a composition according to claim 1 dispersed in a thin layer on an inert support.

7. The film of claim 2 wherein the support is a film forming plastic.

8. The film of claim 2 wherein the binder is a cellulose 6 compound selected from the group consisting of cellulose and cellulose derivatives.

9. The film of claim 2 wherein the 'suppomt is transparent.

10. The process of producing a direct print-out image from originally colorless compounds which comprise prepaving the composition of claim 1 in the form of a thin layer, exposing said layer to visible light and fixing the image which prints out directly as a result of said exposure. 1

11. The composition of claim 1 wherein the heterocyclic ketimide has a five member heterocyelic nucleus.

References Cited by the Examiner UNITED STATES PATENTS 2,895,892 7/1959 Chalkley 9690 X 2,927,025 3/ 1960 Ryskiewicz 969O 2,981,622 4/1961 Chalkey 9()90 X J. TRAVIS BROWN, Acting Primary Examiner.

NORMAN G. TORCHIN, Examiner.

D. D. PRICE, Assistant Examiner. 

1. A COMPOSITION WHICH PRINTS OUT A VISIBLE IMAGE DIRECTLY AS A RESULT OF EXPOSURE TO VISIBLE LIGHT SAID COMPOSITION COMPRISING AN INTIMATE MIXTURE CONSISTING ESSENTIALLY OF: (1) AT LEAST ONE LEUCO COMPOUND SELECTED FROM THE GROUP CONSISTING OF LEUCO COMPOUNDS REPRESENTED BY ONE OF THE FOLLOWING GENERAL FORMULAS 1-((4-(R-N(-R)-)PHENYL)-CH(-R2)-),4-(R-N(-R)-)BENZENE WHEREIN EACH R IS A MONOVALENT RADICAL SELECTED FROM THE GROUP CONSISTING OF H, LOWER ALKYL AND ARYL AND NOT ALL OF THE R''S NEED BE THE SAME AND R2 IS A MONOVALENT RADICAL SELECTED FROM THE GROUP CONSISTING OF H, LOWER ALKYL AND ARYL; AND 2,7-DI(R-N(-R)-),10-R2-ANTHRACENE WHERE Z REPLACES CARBON 9 AND 2,7-DI(R-N(-R)-)ACRIDINE WHERE Z REPLACES CARBON 9 WHEREIN EACH R HAS THE SAME MEANING AS INDICATED ABOVE AND Z REPRESENTS A MEMBER SELECTED FROM THE GROUP CONSISTING OF O, S, SE AND -NH, AND R3 IS A MONOVALENT RADICAL SELECTED FROM THE GROUP CONSISTING OF H, ALKYL AND ARYL; AND (2) AT LEAST ONE COLORLESS NITROGEN-CONTAINING ORGANIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF BENZOTRIAZOLES AND HETEROCYCLIC KETIMIDES IN WHICH THE IMIDE NITROGEN IS ATTACHED TO A RING CARBON IN A HATEROCYCLID NUCLEUS HAVING AT LEAST 5 AND NOT MORE THAN 6 ATOMS. 